Computer Simulation Of Dendrite Growth Into Undercooled Melt Using Phase-field Method

The numerical simulation of solidification microstructure is the frontier domain of the numerical simulation during solidification processes at present. Based on solidification theories, with the help of the advanced techniques such as numerical calculation technique and computer techniques, the numerical simulation of solidification microstructure can be performed to vividly represent the evolvement of solidification microstructure. Dendritic structure is the characteristic structure during solidification process. Among various kinds of numerical simulation techniques, phase-field method is the most viable computational tool, by which complicated dendrite pattern can be easily obtained. In this dissertation, it is the phase-field method that has been applied to the study on dendritic growth into undercooled melt.Firstly, the Micro-Star Integrated Analysis System(MSIAS), which is used to research dendritic growth into undercooled melt, has been developed. MSIAS consists of pre-process module, numerical calculation module and post-process module. The following three points are included, (1) Accomplish the realization of the preprocessor in which various types of parameters including thermal property parameters of material, phase-field parameters, time step and mesh spacing are obtained for numerical calculation module. (2) Realize the discretization of phase-field model based on the even mesh technique,with the numerical calculation convergent, stable, highly accurate and timesaving. (3) Accomplish the development of the post-processor, which visualizes the data of phase-field and temperature field.Secondly, by MSIAS, dendritic growth into undercooled melt has been qualitatively studied. From the viewpoint of common phenomena of crystal growth, effect of phase-field parameters on dendrite pattern has been studied detailedly. At the same time, directional solidification and realistic dendrite patterns like snowflakes are readily reproduced.Thirdly, by MSIAS, dendritic growth into undercooled melt has been quantitatively studied. Concerned with real material, effect of phase-field parameters on dendrite pattern has been studied in detail. By the analysis of features of dendrite tip growth, the surprising agreement between the classical crystal growth theories and phase-field model has been reached.In addition, several key techniques in preprocessor and post-processor of foundry CAE system have been investigated. These techniques, including that of displaying 3-D clipped model in real-time way, that of DIB drawing and that of smoothening the sharp marginal region of a figure, are beneficial to the improvement in function and quality of foundry CAE software.Finally, analysis of real crystal patterns during solidification process of metal material is made to validate the phase-field simulations of this dissertation. The results indicate that real dendrite morphologies agree well with those of phase-field simulations qualitatively.